Modeling And Analysis Of Multi–Phase Permanent Magnet Synchronous Machines: Direct–Drive Electric Vehicle Application

In commercially existing electric vehicles (EVs), power is transferred from the motor to the wheels through a fixed gear mechanical transmission system. However, such a transmission system contributes to a power loss between 2% to 20% of output power of the motor depending on the operating speed and torque of the motor. Therefore, by removing the transmission, a direct–drive EV configuration is obtained with lower component count, improved motor to wheel efficiency and frequency dependent losses. However, challenges in developing a single on–board permanent magnet synchronous machine (PMSM) for such a configuration include high torque density, low torque ripple and high torque per permanent magnet (PM) volume. Therefore, this dissertation proposes a novel PMSM addressing the aforementioned challenges for a direct–drive application. Initially, the design targets, stator and rotor configuration and phase numbers of the PMSM are chosen to satisfy the requirements of a direct drive application. A novel torque and torque ripple model based on multiple reference frames is proposed, in which the torque ripple from spatial harmonics of flux, inductances and the time harmonics of stator currents are included. Using the analytical model, optimal slot–pole combination of the machine is selected based on adaptive gradient descent algorithm. A new consequent pole rotor topology is proposed to improve the torque density and torque per PM volume thereby reducing the usage of expensive rare earth magnets. The proposed PMSM with novel rotor is further improved in terms of torque density, losses and cost by performing an intensive structural optimization based on novel hybrid analytical model, finite element analysis and supervised learning. The optimized PMSM is then analyzed for various drive cycles and performance in terms of torque, speed and efficiency are discussed. A scaled–down prototype of the proposed PMSM is developed and comprehensive experimental analysis in terms of torque ripple, torque–speed characteristics and efficiency are performed under different speeds and load conditions and are compared with the results obtained from proposed analytical model

On the Modeling, Analysis and Development of PMSM: For Traction and Charging Application

Permanent magnet synchronous machines (PMSMs) are widely implemented commercially available traction motors owing to their high torque production capability and wide operating speed range. However, to achieve significant electric vehicle (EV) global market infiltration in the coming years, the technological gaps in the technical targets of the traction motor must be addressed towards further improvement of driving range per charge of the vehicle and reduced motor weight and cost. Thus, this thesis focuses on the design and development of a novel high speed traction PMSM with improved torque density, maximized efficiency, reduced torque ripple and increased driving range suitable for both traction and integrated charging applications. First, the required performance targets are determined using a drive cycle based vehicle dynamic model, existing literature and roadmaps for future EVs. An unconventional fractional–slot distributed winding configuration with a coil pitch of 2 is selected for analysis due to their short end–winding length, reduced winding losses and improved torque density. For the chosen baseline topology, a non–dominated sorting genetic algorithm based selection of optimal odd slot numbers is performed for higher torque production and reduced torque ripple. Further, for the selected odd slot–pole combination, a novel star–delta winding configuration is modeled and analyzed using winding function theory for higher torque density, reduced spatial harmonics, reduced torque ripple and machine losses. Thereafter, to analyze the motor performance with control and making critical decisions on inter–dependent design parameter variations for machine optimization, a parametric design approach using a novel coupled magnetic equivalent circuit model and thermal model incorporating current harmonics for fractional–slot wound PMSMs was developed and verified. The developed magnetic circuit model incorporates all machine non–linearities including effects of temperature and induced inverter harmonics as well as the space harmonics in the winding inductances of a fractional–slot winding configuration. Using the proposed model with a pareto ant colony optimization algorithm, an optimal rotor design is obtained to reduce the magnet utilization and obtain maximized torque density and extended operating range. Further, the developed machine structure is also analyzed and verified for integrated charging operation where the machine’s winding inductances are used as line inductors for charging the battery thereby eliminating the requirement of an on–board charger in the powertrain and hence resulting in reduced weight, cost and extended driving range. Finally, a scaled–down prototype of the proposed PMSM is developed and validated with experimental results in terms of machine inductances, torque ripple, torque–power–speed curves and efficiency maps over the operating speed range. Subsequently, understanding the capabilities and challenges of the developed scaled–down prototype, a full–scale design with commercial traction level ratings, will be developed and analyzed using finite element analysis. Further recommendations for design improvement, future work and analysis will also be summarized towards the end of the dissertation

A review of power electronics equipment for all-electric ship MVDC power systems

Medium Voltage DC (MVDC) distribution Power Systems for all-electric ships (AES) can be regarded as functionally composed of three subsystems, namely the power sources, the load centers and the distribution network. Extensive use of power electronics is required for connecting power sources and load centers to the MVDC bus and for protecting the MVDC power system through properly placed DC circuit breakers. In this paper, an overview is given of the power electronics equipment found in the literature and on the market that could be suitable for use in future AES MVDC power systems. Some industrial experiences regarding DC generator systems, energy storage apparatus and solid-state DC circuit breaker prototypes are reported in the paper as examples of state-of-the-art realizations. Different DC/DC converters, which can be employed as solid-state transformers, are also discussed and a structure obtained by combining them is proposed

Investigations of LC Filter Unbalance in an Inverter-Fed Permanent Magnet Synchronous Motor Drives

Permanent magnet synchronous machines (PMSMs) are usually controlled using two-level inverters. The output voltage of the inverter is in the form of the switching pulses between the positive DC-bus voltage and the negative DC-bus voltage. Such voltage waveforms have several adverse effects on the motor. These include, higher stress on winding insulation, higher eddy current losses and acoustic noise. Thus, to overcome these problems, different types of filters, typically LC-filters are used between the inverter and motor terminals to smooth the pulse width modulation (PWM) output voltages of the motor drives. Theoretically, the inductance and capacitance used for the filters are considered identical in each phase. However, in a practical scenario, it is difficult to have identical filter elements for all three phases. This non-ideal condition of filter elements amongst the three phases is considered as filter unbalance. This thesis investigates the impacts of filter unbalance on the PMSM drive system. Specifically, a comprehensive model of the motor drive system considering filter unbalance is proposed and developed at first. With the developed model, conventional field oriented control (FOC) is implemented to investigate the impact of this filter unbalance. A range of filter parameter variation and the corresponding impact on the motor drive including the motor current, torque and speed ripples is then studied in detail. Thereafter, the results obtained from the proposed model are validated through both circuit simulations and experimental tests. Based on the investigation results, this thesis will discuss the allowable parameter variation in the LC filters to limit the motor performance deterioration within the required bounds, which will be beneficial to engineering practice in motor drive area. In addition, this investigation shows that a conventional FOC with proportional integral (PI) controller might not be capable of mitigating the negative impact on the motor due to filter unbalance, for example, the negative sequence current. Therefore, this thesis implemented an adaptive proportional resonant (PR) controller to address negative sequence current and the corresponding impacts. A detailed mathematical framework to develop this proposed controller will also be presented in the thesis. Finally, the proposed adaptive PR controller is extensively evaluated on a laboratory PMSM drive system under different operating conditions

INVESTIGATION OF PERMANENT MAGNET SYNCHRONOUS MACHINES FOR DIRECT-DRIVE AND INTEGRATED CHARGING APPLICATIONS IN ELECTRIC VEHICLES

Electrified vehicles have proven to be potential candidates in the future for disrupting the automotive industry which is dominated by conventional gasoline vehicles. Electric vehicle (EV) technology has evolved rapidly over the last decade with new designs of EV drivetrain systems and components but no specific design has been able to serve as a solution that is affordable, reliable and performance-wise similar to existing gasoline vehicle equivalent. Extended driving range and overall cost of the vehicle still remain major bottlenecks. Understanding the state-of-the-art technologies and challenges in existing electric vehicle powertrain and charging systems, with major focus on permanent magnet synchronous machines & drives, this dissertation presents the following

Design and Application of Electrical Machines

Electrical machines are one of the most important components of the industrial world. They are at the heart of the new industrial revolution, brought forth by the development of electromobility and renewable energy systems. Electric motors must meet the most stringent requirements of reliability, availability, and high efficiency in order, among other things, to match the useful lifetime of power electronics in complex system applications and compete in the market under ever-increasing pressure to deliver the highest performance criteria. Today, thanks to the application of highly efficient numerical algorithms running on high-performance computers, it is possible to design electric machines and very complex drive systems faster and at a lower cost. At the same time, progress in the field of material science and technology enables the development of increasingly complex motor designs and topologies. The purpose of this Special Issue is to contribute to this development of electric machines. The publication of this collection of scientific articles, dedicated to the topic of electric machine design and application, contributes to the dissemination of the above information among professionals dealing with electrical machines

Multi-level-objective design optimization of permanent magnet synchronous wind generator and solar photovoltaic system for an urban environment application

This Ph.D. thesis illustrates a novel study on the analytical and numerical design optimization of radial-flux permanent magnet synchronous wind generators (PMSGs) for small power generation in an urban area, in which an outer rotor topology with a closed-slot stator is employed. The electromagnetic advantages of a double-layer fractional concentration non-overlapping winding configuration are discussed. The analytical behavior of a PMSG is studied in detail; especially for magnetic flux density distribution, time and space harmonics, flux linkages, back-EMF, cogging torque, torque, output power, efficiency, and iron losses computation. The electromagnetic behavior of PMSGs are evaluated when a number of various Halbach array magnetization topologies are presented to maximize the generator’s performance. In addition, the thermal behavior of the PMSG is improved using an innovative natural air-cooling system for rated speed and higher to decrease the machine’s heat mainly at the stator teeth. The analytical investigation is verified via 2-D and 3-D finite element analysis along with a good experimental agreement. Design optimization of electrical machines plays the deterministic role in performance improvements such as the magnetization pattern, output power, and efficiency maximization, as well as losses and material cost minimization. This dissertation proposes a novel multi-objective design optimization technique using a dual-level response surface methodology (D-RSM) and Booth’s algorithm (coupled to a memetic algorithm known as simulated annealing) to maximize the output power and minimize material cost through sizing optimization. Additionally, the efficiency maximization by D-RSM is investigated while the PMSG and drive system are on duty as the whole. It is shown that a better fit is available when utilizing modern design functions such as mixed-resolution central composite (MR-CCD) and mixed-resolution robust (MR-RD), due to controllable and uncontrollable design treatments, and also a Window-Zoom-in approach. The proposed design optimization was verified by an experimental investigation. Additionally, there are several novel studies on vibro-acoustic design optimization of the PMSGs with considering variable speed analysis and natural frequencies using two techniques to minimize the magnetic noise and vibrations. Photovoltaic system design optimization considered of 3-D modeling of an innovative application-oriented urban environment structure, a smart tree for small power generation. The horizon shading is modeled as a broken line superimposed onto the sun path diagram, which can hold any number of height/azimuth points in this original study. The horizon profile is designed for a specific location on the Barcelona coast in Spain and the meteorological data regarding the location of the project was also considered. Furthermore, the input weather data is observed and stored for the whole year (in 2016). These data include, ambient temperature, module’s temperature (open and closed circuits tests), and shading average rate. A novel Pareto-based 3-D analysis was used to identify complete and partial shading of the photovoltaic system. A significant parameter for a photovoltaic (PV) module operation is the nominal operating cell temperature (NOCT). In this research, a glass/glass module has been referenced to the environment based on IEC61215 via a closed-circuit and a resistive load to ensure the module operates at the maximum power point. The proposed technique in this comparative study attempts to minimize the losses in a certain area with improved output energy without compromising the overall efficiency of the system. A Maximum Power Point Track (MPPT) controller is enhanced by utilizing an advanced perturb & observe (P&O) algorithm to maintain the PV operating point at its maximum output under different temperatures and insolation. The most cost-effective design of the PV module is achieved via optimizing installation parameters such as tilt angle, pitch, and shading to improve the energy yield. The variation of un-replicated factorials using a Window-Zoom-in approach is examined to determine the parameter settings and to check the suitability of the design. An experimental investigation was carried out to verify the 3-D shading analysis and NOCT technique for an open-circuit and grid-connected PV module.Esta tesis muestra un novedoso estudio referente al diseño optimizado de forma analítica y numérica de un generador síncrono de imanes permanentes (PMSGs) para una aplicación de microgeneración eólica en un entorno urbano, donde se ha escogido una topología de rotor exterior con un estator de ranuras cerradas. Las ventajas electromagnéticas de los arrollamientos fraccionarios de doble capa, con bobinas concentradas se discuten ampliamente en la parte inicial del diseño del mismo, así como las características de distribución de la inducción, los armónicos espaciales y temporales, la fem generada, el par de cogging así como las características de salida (par, potencia generada, la eficiencia y la distribución y cálculo de las pérdidas en el hierro que son analizadas detalladamente) Posteriormente se evalúan diferentes configuraciones de estructuras de imanes con magnetización Halbach con el fin de maximizar las prestaciones del generador. Adicionalmente se analiza la distribución de temperaturas y su mejora mediante el uso de un novedoso diseño mediante el uso de ventilación natural para velocidades próximas a la nominal y superiores con el fin de disminuir la temperatura de la máquina, principalmente en el diente estatórico. El cálculo analítico se completa mediante simulaciones 2D y 3D utilizando el método de los elementos finitos así como mediante diversas experiencias que validan los modelos y aproximaciones realizadas. Posteriormente se desarrollan algoritmos de optimización aplicados a variables tales como el tipo de magnetización, la potencia de salida, la eficiencia así como la minimización de las pérdidas y el coste de los materiales empleados. En la tesis se proponen un nuevo diseño optimizado basado en una metodología multinivel usando la metodología de superficie de respuesta (D-RSM) y un algoritmo de Booth (maximizando la potencia de salida y minimizando el coste de material empleado) Adicionalmente se investiga la maximización de la eficiencia del generador trabajando conjuntamente con el circuito de salida acoplado. El algoritmo utilizado queda validado mediante la experimentación desarrollada conjuntamente con el mismo. Adicionalmente, se han realizado diversos estudios vibroacústicos trabajando a velocidad variable usando dos técnicas diferentes para reducir el ruido generado y las vibraciones producidas. Posteriormente se considera un sistema fotovoltaico orientado a aplicaciones urbanas que hemos llamado “Smart tree for small power generation” y que consiste en un poste con un generador eólico en la parte superior juntamente con uno o más paneles fotovoltaicos. Este sistema se ha modelado usando metodologías en 3D. Se ha considerado el efecto de las sombras proyectadas por los diversos elementos usando datos meteorológicos y de irradiación solar de la propia ciudad de Barcelona. Usando una metodología basada en un análisis 3D y Pareto se consigue identificar completamente el sistema fotovoltaico; para este sistema se considera la temperatura de la célula fotovoltaica y la carga conectada con el fin de generar un algoritmo de control que permita obtener el punto de trabajo de máxima potencia (MPPT) comprobándose posteriormente el funcionamiento del algoritmo para diversas situaciones de funcionamiento del sistemaLa tesis desenvolupa un nou estudi per al disseny optimitzat, analític i numèric, d’un generador síncron d’imants permanents (PMSGs) per a una aplicació de microgeneració eòlica en aplicacions urbanes, on s’ha escollit una configuració amb rotor exterior i estator amb ranures tancades. Es discuteixen de forma extensa els avantatges electromagnètics dels bobinats fraccionaris de doble capa així com les característiques resultats vers la distribució de les induccions, els harmònics espacials i temporals, la fem generada, el parell de cogging i les característiques de sortida (parell, potencia, eficiència i pèrdues) Tanmateix s’afegeix l’estudi de diferents estructures Halbach per als imants permanents a fi i efecte de maximitzar les característiques del generador. Tot seguit s’analitza la distribució de temperatures i la seva reducció mitjançant la utilització d’una nova metodologia basada en la ventilació natural. Els càlculs analítics es complementen mitjançant anàlisi en 2 i 3 dimensions utilitzant elements finits i diverses experiències que validen els models i aproximacions emprades. Una vegada fixada la geometria inicial es desenvolupen algoritmes d’optimització per a diverses variables (tipus de magnetització dels imants, potencia de sortida, eficiència, minimització de pèrdues i cost dels materials) La tesi planteja una optimització multinivell emprant la metodologia de superfície de resposta i un algoritme de Booth; a més, es realitza la optimització considerant el circuit de sortida. L’algoritme resta validat per la experimentació realitzada. Finalment, s’han considerat diversos estudis vibroacústic treballant a velocitat variable, emprant dues tècniques diferents per a reduir el soroll i les vibracions desenvolupades. Per a finalitzar l’estudi es considera un sistema format per una turbina eòlica instal·lada sobre un pal de llum autònom, els panells fotovoltaics corresponents i el sistema de càrrega. Per a modelitzar l’efecte de l’ombrejat s’ha emprat un model en 3D i les dades del temps i d’irradiació solar de la ciutat de Barcelona. El model s’ha identificat completament i s’ha generat un algoritme de control que considera, a més, l’efecte de la temperatura de la cèl·lula fotovoltaica y la càrrega connectada al sistema per tal d’aconseguir el seguiment del punt de màxima potenciaPostprint (published version